The invention relates to a process and an apparatus for the surgical correction of defective vision or ametropia, particularly that of one or both eyes of living beings, dependent on a corneal curvature in the optical system.
In objective refraction determination (refraction state of one or both eyes) use is made of the fact that in the optical system in the case of an emmetropic or orthoscopic eye the curved cornea and the natural lens essentially refract the parallel incident light beams, so that the focal or intersection point thereof is in the retinal plane. However, if there is a disparity between the refractive force and the axial length of the optical system, then ametropia occurs, whilst in the case of a short-sighted or myopic eye the focal point is in front of the retina and in the case of a far-sighted or hyperopic eye the focal point is behind the retina. If the incident light beams do not form a common focal point (astigmatism), then the curvature of the cornea varies in different directions, so that a so-called distortion occurs.
The primary correction means for such ametropia are essentially spectacles, contact lenses, etc. In the case of extreme ametropia, it is also known to bring about a correction by surgery, e.g. making use of keratoplasty, keratophakia, epikeratophakia, or keratomileusis modifiying the corneal curvature and thereby bringing about a displacement of the focal point of the retina. According to another operative correction process for less severe cases of ametropia, several radial cuts are made in the periphery of the cornea, so that the latter loses curvature radius and therefore has a smaller refractive force. This operative method known as "radial keratotomy" is limited to the myopic eye.
In the aforementioned, traumatic correction processes, the cornea is on the one hand significantly weakened due to the depth of the radial cuts to be made and on the other hand it is not possible to exclude a gradual redevelopment to the preoperative curvature radii of the cornea and consequently a return of the myopic, hyperopic or astigmatic state of the eye.